Sieg SC3 With DRO fitted – Cross Slide Lead screw – Metric or Imperial

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Sieg SC3 With DRO fitted – Cross Slide Lead screw – Metric or Imperial

Home Forums Manual machine tools Sieg SC3 With DRO fitted – Cross Slide Lead screw – Metric or Imperial

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  • #579480
    Robin Pulham
    Participant
      @robinpulham96156

      The material is 6mm acrylic sheet of some kind that I was given a few years ago.

      I was fortunate to get a couple of lengths of 20mm acetal rod, a couple of quite big blocks of acetal and a couple of small sheets of 6mm acrilic.

      I watched a couple of YT videos where one guy had used oil impregnated bronze for his back lash nut and the other had used acrylic sheet. I looked into buying some bearing bronze but near fainted at the cost so went with what I had. It's really a proof of concept and if it proves successful I may make a replacement in brass at some point.

      Regards Rob

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      #579654
      Howard Lewis
      Participant
        @howardlewis46836

        If there are two nuts on a threaded rod, to enable the nuts to move, there will be a clearance between the flanks of the thread. Without that clearance it would be impossible to move the nuts along the thread.

        Pressing two parts together when they are size and size will not allow relative movement. Hence the need for press forces. For a part to be able to move relative to another, clearance must be present

        In fuel injection equipment, there is clearance between the pumping plunger and its bore, albeit of the order of a micron, resulting in a definite force required to overcome friction, even when lubricated by the fuel.

        If clearance between nut and thread is large enough there will be rotational (angular ) movement of the thread until the clearance is taken up, before any linear movement takes placer.. This is the backlash, with which we all have to live.

        If the nuts are forced apart, each nut will move until the clearance is taken up. If the force is great enough, the nuts and thread will be locked together. If the force is reduced, the time will come when the frictional forces between the male and female threads reduce and can be overcome so that linear movement is possible,

        So by exerting a force to separate the two nuts, by means of an adjustable tapered screw, or springs, the force can be regulated until the backlash is reduced to the point where clearances, and frictional forces allow relative movement. How much torque is required to do this will relate to the forces between the two nuts, and the coefficient of friction between nut and threaded rod.

        Howard

        #579818
        Neil Wyatt
        Moderator
          @neilwyatt

          Mechanically pulling the two thread together has the same effect and may be easier to arrange.

          I have seen it recommended to 'tilt' the nut on a mini lathe using the two screws, to remove backlash. I'm sceptical as it will bind at one end of its travel and be loose at the other as the screw isn't supported at both ends.

          Neil

          #579825
          Robin Pulham
          Participant
            @robinpulham96156
            Posted by Neil Wyatt on 11/01/2022 13:35:25:

            Mechanically pulling the two thread together has the same effect and may be easier to arrange.

            I have seen it recommended to 'tilt' the nut on a mini lathe using the two screws, to remove backlash. I'm sceptical as it will bind at one end of its travel and be loose at the other as the screw isn't supported at both ends.

            Neil

            As I understand it the grub screw in the middle acts as the pivot used in conjunction with the two screws to create a tilt to reduce backlash. Hopefully I will have eliminated that.

            Regards Rob

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